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Transcript
3.1 How Changes Occur Naturally in Ecosystems Natural selection - process where individuals with advantages are better able to reproduce and pass along their traits. A salmon with a smaller tail may never have a chance to spawn because it can’t swim to the correct location. It is believed that all the species are descended from one finch species on the mainland. Each species has unique characteristics that allows them to thrive in their own niche, and not compete with other finches for the same resources. Adaptive radiation - a form of natural selection when many different species appear from one original species. Example: The Finches of the Galapagos Islands (off the coast of Ecuador) There are 13 species of finches on the island… ECOLOGICAL SUCCESSION Changes in the biotic characteristics in an area over time. Primary Succession Secondary Succession 1 Steps of Primary Succession 1. Starts with bare rock. 2. Wind carries spores of lichens that can survive on bare rock. 3. Weathering breaks down rock soil begins to form 4. Pioneer species make soil 5. other plants can grow Pioneer Species are the first organisms to survive and reproduce. Examples: Lichens and mosses 6. animals appear 7. a mature community forms A Mature Community (also called a climax community) is stable and only changes slowly over time – Ex. Old growth forests 2 Secondary Succession: when an area already has soil, but has had a disturbance like a forest fire or is clearcut. - it happens more quickly than primary because there is already soil with seeds, insects, worms, etc. There are many disturbances that Might Cause Secondary Succession: 1. Flooding – leads to soil erosion, spread of pollutants and harmful bacteria associated with sewage – climate change and global warming may be increasing incidents of flooding. – could be caused by a tsunami (when huge waves, from large earthquakes, flood coastal areas.) …in our forests there are a lot of old trees, the climate is warming, and the bugs are not dying in the winter. Drought Insect infestation - Most insects are helpful, but when normal conditions change, infestations can occur. - Example: Mountain Pine Beetle: Usually it is not a problem…it helps remove old trees, but…. - Pine beetle has blue stain fungus in its mouthparts, which it transmits to the trees (symbiotic relationship). - Fungus slows down resin production on trees so the beetle can eat the tree more easily. 3 Modeling Succession Activity http://www.mrphome.net/mrp/succession. swf 3.2 How Humans Influence Ecosystems 1. Land use: All of the land around us, even in cities, was once a part of an ecosystem. – We use the land for things like urban development, agriculture, industry, mining and forestry. Sumas Canal The processing and export of resources like lumber, coal and sulphur are very important to BC’s current economy. 2. Resource use: the ways we obtain and use naturally occurring materials. – Most products you use every day involve the use of some natural resources in their production. Human intrusion has caused many BC wetlands to disappear. – Wetlands are special ecosystems that contain completely waterlogged soil for long periods of time. – In the past 100 years up to 70% of the wetlands in the lower Fraser Valley have been lost. Why are they important? - wetlands contain high biodiversity, and filter many impurities out of the water. - they can help prevent flooding by storing water after rainstorms 4 3. Habitat Loss - Because of human expansion, habitats have been lost or fragmented. “Habitat fragmentation” is the splitting of large habitats into many smaller ones, resulting in disrupted natural activities for plants and animals. Habitat loss Habitat fragmentation 4. Deforestation Deforestation is the clearing or logging of forests for human use. – some land is never reclaimed or replanted. – agricultural crops that are planted are often one species = monoculture This reduces biodiversity, and leaves the crop vulnerable to pests or disease. Polycultures, of many plant species, are more economically and biologically diverse. – Deforestation results in soil degradation (moving wind & water erode topsoil & leave bare land behind). Topsoil: the upper layer of soil, is where most of the nutrients, water and air are found for plant growth. – Deforestation is still occurring in many tropical rainforests. 5 5. Agriculture In fields left without crops, water & wind can cause erosion. In wet areas the soil can become compacted. – Soil particles are squeezed together This is due to farm animals or vehicles. There is no room for water or air to enter the soil. 6. Resource Exploitation: = resource use – Humans depend on resource exploitation for jobs, materials, food, shelter and energy. – Exploitation can lead to habitat loss, soil degradation & contamination of water supplies. Many mining and resource exploitations require reclamation efforts. – Reclamation attempts to reduce environmental impacts of exploitation, and tries to restore the original (or at least functional) habitats. – Because of soil compaction water runs off the soil instead of soaking in. causes leaching. – Aeration, which involves removing small plugs of soil, loosens soil & can reduce run-off. Overexploitation: – the extraction of resources until they are gone. Can result in extinction – Example: passenger pigeon Food webs can be greatly affected for long periods of time especially in keystone species (species that greatly influence the population numbers and health of an ecosystem) 6 Sustainability of Ecosystems Reducing Habitat Fragmentation Definition #1: “The ability for an ecosystem to maintain ecological processes”. – ie. the ecosystem stays healthy naturally Definition #2: “People using an ecosystem to meet their needs today without reducing the function or health of the ecosystem in the future” Sustainable practices maintain, or even improve, healthy ecosystems. Returning young coho salmon to rivers near Port Alice can help maintain sustainability. Traditional Ecological Knowledge: In Aboriginal cultures it is passed down from generation to generation. – This knowledge reveals what past condition were like, and also how the ecosystem and humans interact. – Knowledge is found in stories, songs, cultural beliefs, rituals, community laws and traditional practices. – Current ecological restoration and usage guidelines often involve this traditional knowledge from Aboriginal representatives. Traditions such as the “Spring burn” allow for ecological renewal. Fire suppression, enforced in BC for over 100 years, has led to recent issues like the mountain pine beetle infestation and huge wildfire losses. 7 Invasive Species 3.3 How Introduced Species Affect Ecosystems Native species naturally live in an area. Introduced species (aka foreign species, non-native species, exotic species or alien species). – they have been introduced accidentally (& on purpose) here over the past 400 years due to immigration. – Many of these species are harmless, even beneficial. Invasive species: are introduced species that often take advantage of their new habitat. – They may have no predators, are aggressive competitors, & reproduce fast. Eg. Purple Loosestrife, negatively impacts native species, and often reduces biodiversity as a result. The sea lamprey arrived in the Great Lakes via the canals and St. Lawrence Seaway over 50 years ago, making its way around Niagara Falls that at one time protected the Great Lakes from many east coast species. They do millions of dollars of damage to Great Lakes fisheries each year. The European leaf-feeding beetle (left), and the Purple Loosestrife. The Impact of Introduced Species Competition: one species takes away resources from another. Predation: if the invasive species is a predator, it may have a huge advantage, as the native species may have no methods to survive. The Norway rat escaped from early European explorer and fur-trading ships. On Queen Charlotte Islands, they have caused a decline in groundnesting sea birds, such as ancient murrelets and puffins, by eating their eggs and young. 50 breeding pairs of the European Starling were brought to BC in the late 1800’s. It now out-competes western bluebirds for nesting habitat. The American Bullfrog was brought to BC in the 1930’s by restaurants for their legs. It has since taken over the habitats of native frogs. West Nile virus was recently introduced to the United States in 1999, when it started causing deaths in birds and illness in humans in New York City. It is a vector borne disease, carried by the mosquito. Disease & Parasitism: by weakening certain species, a microorganism invading an ecosystem can drastically alter the entire ecosystem and the niches within it. 8 Habitat Alteration: some invasive species can change the physical structure of the ecosystem by digging, burrowing, blocking sunlight or changing the chemistry of the ecosystem. Eurasian Milfoil was first identified in Okanagan Lake in 1970. It forms wide, dense mats at lake surfaces, cutting off sunlight to organisms below and interfering with recreational activities. It can grow from plant fragments, which are often spread by boats. It often takes human intervention to save established ecosystems. - The Garry Oak Ecosystem Recovery Team (GOERT) is trying to save several ecosystems in BC because Garry Oak trees are a keystone species - Scotch broom, English ivy and other plant species are its biggest threats. 9